From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-9.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0E66FC5DF62 for ; Wed, 6 Nov 2019 07:31:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BC49C2173E for ; Wed, 6 Nov 2019 07:31:44 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b="UeYFaws6" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731218AbfKFHbn (ORCPT ); Wed, 6 Nov 2019 02:31:43 -0500 Received: from mail-m974.mail.163.com ([123.126.97.4]:51108 "EHLO mail-m974.mail.163.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729787AbfKFHbn (ORCPT ); Wed, 6 Nov 2019 02:31:43 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=From:Subject:Date:Message-Id; bh=10j9yC2LKZ4Yu8yJAT 38Az579fi88WXpZdGmSsenJPQ=; b=UeYFaws6OMq6xy765lPDJs+n7oC6z4TtQl vbRk9uEz0iZ5qE5YN/NlX6LAaS6zPv86MgtPDw1tUc0aA3+UGA6XpunNBUnojJrF 09FfMGQxsNFdoFNXRD1fYqiB3jW7aUpe7OYDqcjV3jUpHLrIU5rbsXXXcJ/Aeqzm R+rHk2M8c= Received: from localhost.localdomain (unknown [202.112.113.212]) by smtp4 (Coremail) with SMTP id HNxpCgCXRjG8dsJd0yl7BQ--.263S3; Wed, 06 Nov 2019 15:31:26 +0800 (CST) From: Pan Bian To: Zhenyu Wang , Zhi Wang , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , David Airlie , Daniel Vetter Cc: intel-gvt-dev@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Pan Bian Subject: [PATCH] drm/i915/gvt: fix dropping obj reference twice Date: Wed, 6 Nov 2019 15:31:07 +0800 Message-Id: <1573025467-18278-1-git-send-email-bianpan2016@163.com> X-Mailer: git-send-email 2.7.4 X-CM-TRANSID: HNxpCgCXRjG8dsJd0yl7BQ--.263S3 X-Coremail-Antispam: 1Uf129KBjvdXoWrtrW3tr1DXFWxKrWfKw1kGrg_yoWkurbEkr WYqF17CrZrKFs09r1jyr9rAas2gF4UZFW8W3y7t34kA342kw1DZFZ5Zr15Zr18uF4UAFZx AF1xury3ZFWF9jkaLaAFLSUrUUUUUb8apTn2vfkv8UJUUUU8Yxn0WfASr-VFAUDa7-sFnT 9fnUUvcSsGvfC2KfnxnUUI43ZEXa7IU1xwIPUUUUU== X-Originating-IP: [202.112.113.212] X-CM-SenderInfo: held01tdqsiiqw6rljoofrz/xtbBUQ5lclaD5JcnsgAAs7 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The reference count of obj will be decremented twice if error occurs in dma_buf_fd(). Additionally, attempting to read the reference count of obj after dropping reference may lead to a use after free bug. Here, we drop obj's reference until it is not used. Signed-off-by: Pan Bian --- drivers/gpu/drm/i915/gvt/dmabuf.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/gvt/dmabuf.c b/drivers/gpu/drm/i915/gvt/dmabuf.c index 13044c027f27..4bfaefdf548d 100644 --- a/drivers/gpu/drm/i915/gvt/dmabuf.c +++ b/drivers/gpu/drm/i915/gvt/dmabuf.c @@ -498,8 +498,6 @@ int intel_vgpu_get_dmabuf(struct intel_vgpu *vgpu, unsigned int dmabuf_id) goto out_free_gem; } - i915_gem_object_put(obj); - ret = dma_buf_fd(dmabuf, DRM_CLOEXEC | DRM_RDWR); if (ret < 0) { gvt_vgpu_err("create dma-buf fd failed ret:%d\n", ret); @@ -524,6 +522,8 @@ int intel_vgpu_get_dmabuf(struct intel_vgpu *vgpu, unsigned int dmabuf_id) file_count(dmabuf->file), kref_read(&obj->base.refcount)); + i915_gem_object_put(obj); + return dmabuf_fd; out_free_dmabuf: -- 2.7.4